xcoffins – Rich boxed material for LaTeX 3

Coffins are boxes which con­tain type­set ma­te­rial. Along with the
box it­self, the cof­fin struc­ture holds in­for­ma­tion about the size
and shape of the box, and align­ment in­for­ma­tion in the form of a
set of “poles” (hor­i­zon­tal and ver­ti­cal lines at par­tic­u­lar
po­si­tions de­fined rel­a­tive to the box). The points where these
poles in­ter­sect are “han­dles”, which are the points used to de­fine
the plac­ing of a cof­fin.

The pack­age pro­vides a de­sign-level in­ter­face to the LaTeX 3
ker­nel func­tions which pro­vide coffins.